Yersinia enterocolitica infection presents a wide clinical spectrum; in infants and young children it usually presents as uncomplicated acute diarrhea, while in older children and adolescents it more frequently presents as terminal ileitis and/or mesenteric adenitis. We describe two infants who developed terminal ileitis complicating Y. enterocolitica infection, which is exceptionally rare. The clinical, laboratory and radiologic findings are described and ultrasound study is emphasized as a simple and reliable tool for investigation of terminal ileitis.